Ignition transformer



Feb" 25, 1936. ROSE ET AL 2,032,151

IGNITION TRANSFORMER Filed June 2, 1955 INVENTORS Hen Jeri A. Rose & A/berf J. Mas/in w- &

Maw.

ATTORNEY Patented Feb. 25, 1936 UNITED STATES PATENT OFFlCE IGNITION TRANSFORMER Application June 2, 1933, Serial No. 673,976

9 Claims.

Our invention relates to an ignition transformer, and particularly to a transformer coil for ensuring ignition of parallel anodes in separate rectifier tanks.

In the operation of vapor electric devices, it has been found that relatively small capacity rectifiers500 to 1000 KWhave an inherent advantage over larger sizes of rectifiers. It has therefore been found more advantageous to construct arc chambers of a size having the greatest relative efiiciency and to parallel a plurality of such small efiicient arc chambers to produce rectifiers of large capacity. In paralleling these are chambers it has been found that greater efficiency and simplicity can be procured by feeding the complete rectifier from a single transformer winding.

In operating a plurality of rectifier sections from a single transformer winding it was found that frequently one of the parallel sections would fire before the others. As a consequence, the ionizing potential in the non-firing section was reduced to the amount of the arc-drop in the firing sections. Frequently, this small ionizing potential was insufiicient to fire the idle rectifier section with the result that the entire load was concentrated in one or more of the parallel devices, resulting in serious overload on the active sections.

It is an object of our invention to provide a paralleling transformer for so interlocking the circuit to the parallel anodes that when one of a plurality of parallel sections takes the load prior to the ignition of the remaining sections, a high voltage compared to the arc-drop will be impressed on the anodes of the idle sections to insure firing or pick-up of load by all sections.

The ignition transformer of our invention comprises a multi-section coil having a mid-tap connected to a phase terminal of the rectifier transformer, and a plurality of terminals connected to parallel anodes in separate arc chambers. A suitable magnetizable core is associated with the paralleling coil, said core having means to prevent saturation of the core by unbalanced current in the various sections.

Other objects and advantages will be apparent from the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic view of a rectifier embodying our invention;

Fig. 2 is a schematic illustration of a preferred type of ignition transformer; and,

Fig. 3 is a graphical illustration of the potentials available for igniting the idle section.

The apparatus according to our invention consists of a rectifier l comprising a plurality of arc chambers designated A and B, each of the are chambers has a cathode H, said cathodes being connected together and adapted to be connected to one side l2 of a direct current circuit. Each tank is provided with a plurality of anodes I, 2,

3, 4, 5 and 6.

The rectifier I0 is fed through a transformer having a, polyphase winding I4 connected to an alternating current line l5, and a feeding wind ing l6 having phase windings l, 2', 3', 4, 5, and 6' for connection to the corresponding anodes. The phase windings of the transformer are connected in multiple star and separated by an interphase transformer I! to provide a double three-phase winding. Each phase terminal of the polyphase feeding winding I6 is connected to parallel anodes by means of our ignition transformers.

Our transformers consist of coils 20, each having a plurality of sections and a mid-tap for connection to a phase terminal of the transformer IS, the terminals of coils 20 being connected to parallel anodes in separate arc chambers. The numerals I", 2", 3", 4", 5" and B" have been associated with the various windings 20 to facilitate the tracing of the connections from the various anodes I to 6 through to the associated windings I to 6'. The sections of the multisection coils 20 are associated with a suitable magnetizable core 22, the sections being so wound with relation to the core that a current through one section will set up a fiux in the core 22 to induce, by auto-transformer action, an impulse of voltage in the remaining sections of the coil 26. In this manner the flux set up by current fiow in each section of the coil 20 is opposed by the flux set up by current fiow in the remaining sections. Consequently, when the current is substantially the same in the coil sections 2!! of the auto-transformer, the resultant core flux is substantially zero.

The reactance of the ignition transformers when only one are chamber is firing is such that the ignition transformers rob the circuit of most of its voltage and impress it on the anodes of the idle arc chambers.

Assume a clockwise rotation of voltage in the phase windings and that section A is firing while section B has failed to fire. As the voltage dereases in phase 5, for instance, the voltage in phase I increases and the total voltage available the end of the commutating period this voltage is sufficient to supply the required. ignitien potential to the anodes of the idle section.

:2 for transferring the are from anode 5 ts anode l is (ii- 65, 7

Since anode 5 in tank A is firing, anode I in 1 tank A will also fire and the instantaneous voltage from anode 5 to anode is d d I d r-' s= agg 55; 1 15? where L5 is the unbalanced inductance of the ignition transformer in phase 5, I5 is the inductance of the winding of phase 5of the main transformer, I1 is the inductance of phase I of the main transformer, and 121 is the unbalanced inductance of the, ignition transformer in phase I since L5=L1 and 11:15

" By construction the unbalanced inductance of the ignition transformer is made several times, preferably ten times, that of the supply trans= former? By virtue of the construction the greater portion of the commutating voltage 6'165 is absorbed by the ignition transformer so that at The potential to cause striking of the arc to E anode I ofsection B is the instantaneo is poten- 1 tialfbetween the idle anode and the. cathode.

Since the cathodes I I are tied together, the voltage difference from B'cathode to anode I.B is

" the arc drop in A, the reactancelvoltage flux resulting in. anincrea'sed and more rapid in that half of the winding Zlftraversed by current in anode I'-A. Since this reactance volt age is opposed to the;;flow of current' in anode I--'A,-it is'positive with respect to anode IB'.

A voltage is induced in the remaining section of a coil of ignition transformer equal to l, i i V 1 5;

whichis also positive with respect to anode I-B, so that the total firing potential of anode I-B is arc drop of section A. 2

Inerder to eontrolthe magnetic characteristic of the devicei and' to prevent saturation of the core22, by currents flowing in onef'section'iof the coil 26, before the desired commutation volt-' age is'reached, we prefer to provide the score 22 with a suitable non-magnetic portioni such as an air gap 23. The air gap 23 is so proportioned that the reactance of the coil 20 is stihstantially failure ofv a section to fire results in cyclic flux reversals in the core 22. This arrangement increases thereifectiveness of the ignition transformer by taking advantage of the polarity of the residual flux established by the previous period of current conduction. The start of the next period of conduction, reverses the residual flux change andresultant voltage concentration than would be the case for anode connections which do not give flux reversals in the corezl For purposes of simplicity and illustration, we i have shown acore type construction in the ignition transformers according to Fig, 1. However, we prefer'to use ashfell type core 25 as shown in Fig. 2, and to dividejeach section of the ignition coils 2i] and to place the segments of the multisection coils on opposite sides of an'air gap 26 in the centralgleg of the shell core 25.

We have foiind that the shell type core possess- 7 es several advantages, namely, ease of assembly,

improved bracing, decreased noise and improved cooling facilities.

Ingmany cases, it will be found desirableito provide the air gap in the core with a suitable magnetic bridge 2'I. 7

While we have shown and described a specific embcidiment of our invention, it is'apparent that changes and modifications may be made therein without departing'from the spirit and scope of the invention. We desire, therefore; that only suchlimitation's shall be imposedas are contained in the accompanying claims of as may be necessitated by the prior art.'

' We claim as our invention: 7 .7 1. A conversion systemc omprisirig a source of alternating current,parallel vapor electric devices, a cathode in each of said'devices, said cathodes being connected together, a plurality of anodes in each of said devices, two anodes being connected to a common'plfiase terminal of said current source, said anodes being in separate devices and means to compel parallel operation of the anodes comprising a two-section ignition coil, the terminals of said coil being connected to the parallel anodes, a ta'pin said coil connected to the phase'terminal snpplying said anodes, a mag' netizable core associated with said coil, each of.

the sectionsof said. coil being adapted to generate opposing flux in said core, a second two-section coil associated with said core; the terminals be 'ing connected to parallel anodes in the same devices as the anodes connected to the first" mentioned coil,'the mid-tap of said second c'oil being connected to a phase terminal other than that connected to said first coil, the sections of said second coil being adapted to generate a flu)? in opposite direction to the corresponding 7 sections of the first 'coil. e V 2. A mercury arc'converter system comprising a transformer, parallel arc chambers connected to said transformer, said are chambers having a" common cathode connection,'each pliase'terminal of said transformer supplying current to two anodes, said anodes being in separate arc chambers, a coil havinga middle terminalconnection;

to a phase terminal of the transformer, and two end terminals eachconneclfied to an anode, a core associated With said coil, means for'preventing' saturation of said core, said c'oil being wound on 7 said core so that c rrent between the phase terminal and any one anode terminal induces an impulse of voltage to the remaining anode. V

3. A rectifier system comprising two rectifier units, a transformer for supplying current to said with said ignition transformer, said core having 7 an air gap to prevent saturation at. normal currents, a second coil on said core, said second coil being connected to' a transformer terminal different from that of the first coil and having its ends connected to an anode in each rectifier.

4. In a polyphase multi-tank mercury-arc rectifier system, a plurality of anodes in each tank and means for compelling parallel operation of the rectifiers comprising a winding having terminals connected to two anodes in separate rectifier tanks, a mid-tap in said winding adapted to be connected to a phase terminal of a rectifier transformer, a magnetizable core in said windings, said core having an air gap therein to control the saturation characteristic of the core, said winding having a high reactance when current is flowing to one anode for impressing a high firing potential, compared to the arc-drop of. the rectifier, on the idle anode.

5. In a polyphase multi-tank mercury-arc rectifier system, a plurality of anodes in each tank, means for compelling simultaneous operation of the rectifiers comprising a winding having terminals connected to two anodes in separate rectifier tanks, a mid-tap in said winding adapted to be connected to a phase terminal of a rectifier transformer, a magnetizable core in said windings, said core having an air gap therein to control the saturation characteristic of the core, said winding having having a high reactance when current is flowing to one anode for impressing a high firing potential on the idle anode, a second winding associated with said core, said second winding having terminals connected to anodes in the same tanks as the anodes connected to said first mentioned winding.

6. A vapor electric system comprising a source of alternating current having a plurality of phase terminals, parallel arc-chambers, a plurality of anodes in each of said are chambers, an anode in each chamber being fed from the same phase terminal of the supply source, an ignition transformer connected between each phase terminal and the parallel anodes fed thereby, said transformer comprising a multi section coil, each section being connected to an anode and to the phase terminal of the supply source, a core associated with said coil, said core having a substantially non-magnetic portion for controlling the reactance of the coils, said coil being adapted to generate a voltage of the order of several times the arc drop in said arc-chambers when one of the anodes fails to fire.

'7. An ignition transformer for insuring pickup of parallel sections of a two-section arc-discharge device comprising a plurality of anodes in each of said sections, an ignition transformer winding having terminals connected to an anode in each of said sections, a magnetizable core associated with the winding, means for supplying current through said transformer to said anodes, said transformer being so connected that failure of one of said anodes to pick up impresses an impulse of voltage thereon, a second ignition transformer winding associated with said core, said second winding being connected to anodes in the same devices as said first mentioned winding, said windings being so connected to said anodes that continued failure of one of the sections to pick-up results in cyclic reversals of the flux in said core.

8. In an electric-arcv conversion system having a plurality of parallel arc-chambers, each arcchamber having a plurality of electrodes, a source of current having a plurality of phase terminals adapted to be connected to saidelectrodes, each of said terminals being connected to an electrode in each of said arc-chambers, a current device for insuring pick-up of the parallel electrodes in sepa-- rate arc-chambers comprising a winding having a mid-terminal connected to a phase-terminal of said source and end terminals connected to said parallel electrodes, a magnetizable core having a plurality of legs, said core being linked with said winding, a substantially non-magnetic section in said core, the portions of said winding between said mid-tap and said end terminals carrying current in such direction that if one of said parallel electrodes fails to carry current, a voltage im pulse will be induced in that portion of the coil connected to the idle electrode.

9. In an electric-arc conversion system having a plurality of parallel arc-chambers, each arcchamber having a plurality of electrodes, a source of current having a plurality of phase terminals adapted to be connected to said electrodes, each of said terminals being connected to an electrode in each of said arc-chambers, a current device for insuring pick-up of the parallel electrodes in separate arc-chambers comprising a winding having a mid-terminal connected to a phase terminal of said source and end terminals connected to said parallel electrodes, a magnetizable core having a plurality of legs, said core being linked with said winding, a substantially non-magnetic section in said core, the portions of said winding between said mid-tap and said end terminals carrying current in such direction that if one of said parallel electrodes fails to carry current, a voltage impulse will be induced in that portion of the coil connected to the idle electrode, a second winding similar to said first-mentioned winding linked with said core, said second winding having its mid-tap connected to a phase terminal of said source different from that connected to said first winding and having its end terminal connected to electrodes in the same arc-chambers as said first winding, said windings being so connected to their respective electrodes that continued failure of one arc-chamber to carry current results in voltage impulses of increased magnitude being applied to the idle electrode.

HERBERT A. ROSE. ALBERT J. MASLLN. 

